In recent years, because of significant progress of image displaying technologies, there has been developed a technology for displaying three dimensional images, in addition to a technology for displaying two dimensional images. The technology for displaying three dimensional images can be used in a remarkably wide range of fields, such as entertainments, medical fields, and electronic catalogs/advertisements.
As a technology for displaying three dimensional images, a polarized glasses method is known. When employing this method, a right-eye image and a left-eye image are displayed alternately at every single dot line on a display screen, and linearly polarizing filters are provided in front of the images. In so doing, the linearly polarizing filter for a left-eye image is provided in front of the left-eye image, and the linearly polarizing filter for a right-eye image is provided in front of the right-eye image, whereby light of the left-eye image and light of the right-eye image are converted by the respective linearly polarizing filters into linearly polarized lights whose polarizations are orthogonal to each other. Then, prepared are polarized glasses configured such that a polarizing plate having a polarization axis for the left-eye image is attached to a left-eye lens, and that a polarizing plate having a polarization axis for the right-eye image is attached to a right-eye lens. When a viewer wearing the polarized glasses views the displayed images, the left eye receives only the left-eye image, and the right eye receives only the right-eye image. This causes the left eye to perceive only the left-eye image, and causes the right eye to perceive only the right-eye image, whereby the viewer recognizes a three dimensional image.
While the polarized glasses method mentioned above requires a viewer to wear polarized glasses, technologies for displaying a three dimensional image without requiring polarized glasses have been developed in recent years. One of those technologies is a parallax barrier method. When employing this method, a right-eye image and a left-eye image are displayed alternately at every single dot line on a display screen, and a parallax barrier with slits made at predetermined intervals therein is positioned in front of the images. When a viewer views the displayed images, the parallax barrier blocks the right-eye image from being visible to the left eye, and blocks the left-eye image from being visible to the right eye. This causes the left eye to perceive only the left-eye image, and causes the right eye to perceive only the right-eye image, whereby the viewer recognizes a three dimensional image.
Alternatively, a lenticular lens method is also a technology for displaying a three dimensional image without requiring polarized glasses. When employing this method, a right-eye image and a left-eye image are displayed alternately at every single dot line on a display screen, and a lenticular lens is provided in front of the images. When a viewer views the displayed images, only the left-eye image enters the left eye, and only the right-eye image enters the right eye by the effect of the lenticular lens. This causes the left eye to perceive only the left-eye image, and causes the right eye to perceive only the right-eye image, whereby the viewer recognizes a three dimensional image.
These three methods mentioned above use binocular parallax to enable a viewer to perceive a displayed image three-dimensionally. Having said that, since all of these methods make use of a flat screen, displaying a three dimensional image on a curved surface is not possible. In order to deal with this problem, technologies for displaying a three dimensional image on a curved surface are disclosed in Patent Literatures 1-3.
Patent Literature 1 discloses such a configuration that a three dimensional video display device, which is configured such that a plurality of columns of LEDs (light emitting diode) are aligned on the circumference of the device, is rotated so as to induce an afterimage effect. The three dimensional video display device is rotated at an appropriate rotation speed, and appropriate display signals are sent to individual LEDs in sync with the rotation speed. Each LED is provided with a slit, and beams of light emitted from the plurality of LEDs are radiated out of the slits with a predetermined pitch angle for creating parallax. Then, the beams of light from the plurality of LEDs enter the eyes of a viewer respectively, and the viewer recognizes, by the effect of binocular parallax, a colored three dimensional image in spaces in front of and behind display units. It should be noted that, by moving around the three dimensional video display device, the viewer can view the three dimensional image from all around the substantially cylindrical three dimensional video display device.
Patent Literature 2 discloses a technology for displaying a three dimensional image by using a screen that rotates at high speed. When employing the technology disclosed in the present Patent Literature, there are prepared in advance slide images viewing the center of a display target from a plurality of viewing points provided, at regular intervals, on a proper circumference surrounding the display target at the center thereof. Then, the slide images are projected in series on a fast rotating screen by using reflecting mirrors. By continuously repeating this process, an afterimage effect on naked eyes is induced, whereby the eyes recognize a three dimensional image of the display target on the screen. This technology disclosed in the present Patent Literature is also applicable to projection of moving images.
Patent Literature 3 discloses a three dimensional video display device that has rotatable display plates including LED units positioned in spirals and that has, on the back sides of the display plates, a screen reflecting an image projected from an image projector. Each of the plurality of LED units emits light and stops to emit light in correspondence with a three dimensional image to be displayed as the display plate rotates. This makes it possible to view, by an afterimage effect, the three dimensional image in a light emitting displayable area in front of the display plate. Then, the background of the three dimensional image displayed in the light emitting displayable area is projected from the image projector on the screen. This allows the image displayed by the rotation of the display plates and the background image on the screen to be viewed while both images are overlapping each other. The technology disclosed in the present Patent Literature makes it possible to display, by using a display created by light emission and a display created by image projection together, a realistic three dimensional image constituted by a combination of still images and moving images.
A technology disclosed in Patent Literature 4 exercises ingenuity that renders even a higher degree of realistic sensation. The present Patent Literature discloses such a configuration that image data indicative of an image surrounding a viewer is split into segments that are displayed on a plurality of display devices positioned around the viewer. Each display device produces and displays such an image as to be viewed when the viewer views toward the display device. This allows the viewer to receive, from each of the display devices, an image of a virtual-space surrounding the viewer, whereby the viewer can experience a high degree of realistic sensation and immersion as if the viewer were in fact present in the midst of the three dimensional virtual-reality space.